1. Field of the Invention
This invention relates to apparatus for delaying opening of doors. More particularly, this invention relates to apparatus for delaying opening of doors such as emergency exit doors or fire doors while providing a signal indicating that an attempt is being made to open the doors.
2. General Considerations and Prior Art
The above-identified patent applications each relate to the concept of delaying opening of a door while sounding an alarm or providing another signal indicating that an attempt to open the door is being made. As is set forth in each of the above-cited patent applications this concept is useful in solving the conflict between fire officials, fire regulations and security officials. Generally, fire codes specify that certain doors cannot be locked with respect to the inside of a building when the building is occupied so that occupants can escape if a fire or other emergency situation arises. However, the chronic crime problem has caused people concerned with security to lock these doors with padlocks and chains. By providing doors with a delay which under ordinary circumstances secures the door for a period of time and which under emergency circumstances releases the door immediately, a satisfactory solution to the fire-security conflict is provided.
Under certain circumstances it may be desirable to divorce the unlatching structure of a door such as an emergency exit door from the delay structure so that the delay structure can be retrofitted on existing doors which already have their own hardware. Such an approach is disclosed in co-pending patent application Ser. No. 051,724--Magnetic Emergency Exit Door Lock System and co-pending patent application Ser. No. 089,398--Door Check Type Delay. Both of these approaches have disadvantages which may forestall their use. With the magnetic arrangement, there is a problem of residual magnetism which must be overcome in order to open a door even after the magnet is de-energized. In the door closure type of delay device, the door is never completely free of the door closure jamb which can interfere with ordinary operation of the door wherein the door operates in a non-delay mode. Accordingly, there is a need for a delay apparatus which can be easily applied to emergency exit doors as a retrofit for existing installations or as an accessory for planned installations which use conventional latching and locking hardware.